The present invention relates generally to networked building automation and control systems. More particularly, the invention relates to an object-oriented communication system employing surrogate objects to enable distributed-object components of the building automation system to interoperate.
The trend today in building automation systems is to move away from centralized to distributed control. Control functions that were once handled by a central controller are now being increasingly handled by distributed controllers connected to a computer network. Unlike conventional data processing networks, building automation system networks typically employ a large number of low cost microcontrollers, each dedicated to handling a different building automation function. Typically these controllers contain a microprocessor and the minimal complement of random access memory needed to perform the local task. Thus, although architecturally similar to a local area network in an office environment, the building automation network is considerably different when the capacity and function of the individual nodes are considered.
To illustrate the difference, a typical office environment computer or workstation has a large complement of random access memory and usually an even larger disk storage. Thus the office computer or work station is designed to run a variety of different application programs, often concurrently. In contrast, the "computer" at a typical node on a building automation network might comprise a far less powerful processor with minimal random access memory and no disk storage. The processor's function might be to control a single device, such as a damper in an air-handling unit.
Although the individual controllers at each node in a building automation network lack the computing power of an office workstation, they represent considerable computing power when considered collectively. The problem control engineers face today is how to harness that computing power. If these individual controllers could be integrated to work collectively they could perform sophisticated functions formerly possible only by using a powerful central controller. The difficulty has heretofore been how to integrate these controllers so that collectively they may perform sophisticated functions.
The present invention makes such integration possible through a powerful distributed-object communication system. The invention provides an architecture in which sophisticated building automation applications may be constructed from a plurality of comparatively simple standard building automation software objects. These objects, many of which are quite small and perform a singular purpose, communicate with one another through special surrogate objects provided by the communication system of the invention. The surrogate objects serve as the glue that binds the other standard objects into a complex building automation application and allow portions of the system to reside on physically separate servers. The surrogate objects allow objects to locate one another across a distributed network.
For a more complete understanding of the invention, its objects and advantages, reference may be had to the following specification and to the accompanying drawings.